1. Field
Exemplary embodiments of the present invention relate to a surface treatment method for a semiconductor device, and more particularly, to a surface treatment method that may prevent patterns from leaning, being bent, or collapsing in a semiconductor device.
2. Description of the Related Art
As semiconductor devices are integrated higher and higher, the height of patterns on a substrate becomes increased while the occupying area of the patterns on the substrate and the gap between the patterns are decreased. Examples of the patterns having a High Aspect Ratio (HAR) include Shallow Trench Isolation (STI) patterns of a flash memory device or capacitor patterns of a Dynamic Random Access Memory (DRAM) device.
When a rinsing process and a drying process are performed on the HAR patterns after a cleaning process or a wet etch process is performed, the HAR, patterns may lean, be bent, or collapse due to the stress caused by the surface tension of a cleaning solution or a rinsing solution and applied to the surface of the HAR patterns.
FIGS. 1A to 1C illustrate a problem of conventional HAR patterns.
Referring to FIG. 1A, a rinsing process is performed using a rinsing solution 3 on a substrate 1 where a plurality of patterns 2 is formed. The rinsing solution 3 may be deionized water. The rinsing process may be performed following a cleaning process or a wet etch process on the substrate 1.
Referring to FIG. 1B, a drying process is performed to remove the rinsing solution 3 remaining on the surface of the substrate 1.
Referring to FIG. 1C, stress is applied to the surface of the patterns 2 due to the surface tension of the rinsing solution 3 used in the rinsing process, causing the patterns 2 to lean, be bent, or collapse.
FIG. 2 illustrates the stress applied by the rinsing solution 3 to the patterns 2 over the substrate 1 during the drying process. Herein, the maximum stress applied to the patterns 2 is represented by the following Equation 1.σmax=6γ·cos θ·A2/D  Eq. 1
where γ denotes the surface tension of the rinsing solution 3,
θ denotes a contact angle of the rinsing solution 3 with respect to the surface of the patterns,
A denotes an aspect ratio (the height of the patterns (H)/the width of the patterns (W), and
D denotes the distance between the patterns 2.
To alleviate the stress applied from the rinsing solution 3 to the patterns 2 during the drying process in the above Equation 1, the aspect ratio A may be decreased or the distance D between the patterns 2 may be increased. However, since decreasing the aspect ratio A and increasing the distance D between the patterns 2 are all against increasing the integration degree, they may not be considered as a method for alleviating the stress applied from the rinsing solution 3 to the patterns 2. Therefore, to reduce the stress, the surface tension γ of the rinsing solution 3 is made to decrease, or the contact angle θ of the rinsing solution 3 with respect to the surface of the patterns 2 is made close to 90°.
Capacitor patterns of a DRAM device have a tendency of decreasing pattern width and decreasing gap between the patterns to obtain fine patterns, while having their height increasing to secure a dielectric rate. The aspect ratio is approximately 40 or higher.
According to a conventional technology, a nitride floating cap (NFC) is deposited in the upper portion of the HAR patterns to protect the HAR patterns from leaning or being bent during the drying process of the HAR patterns. In this case, however, leaning or bending may occur in the middle of the HAR patterns, as the height of the patterns increases.
To mitigate this concern, a method of performing a rinsing process by using heated isopropyl alcohol (IPA) as a rinsing material and then performing a drying process has been suggested. Since the surface tension of isopropyl alcohol (IPA) may be approximately 20 dyne/cm, which may be much lower than the surface tension of water, i.e., approximately 70 dyne/cm, the above-described concern may be somewhat reduced.
However, as semiconductor devices are integrated more and more, the aspect ratio of patterns may increase higher and higher. Moreover, the technique using heated isopropyl alcohol (IPA) may be facing limitation. To protect patterns from leaning or being bent, a double supporter may be used, which may lead to an increase in the number of procedural steps and production cost.
Therefore, it may be required to develop a method for minimizing the stress applied from a rinsing solution to patterns in order to prevent the patterns from leaning or being bent in a drying process following a cleaning or rinsing process.